Yes that is correct. However an infringement on reality is what Hegel did to Kant, when he materialized the idea. In Itself ?

Now let's not go that fast, and use meaning theory to reject any justification as regards to the idea as material.Common sense for the positivist position may be akin to a naive reality corresponding to the idea that what reality is , is perceivable.

But the unseen or that which the idea of subjects produce , gain legitimacy in the unseen , that , which is too small or too far away. The idea of those things if they can be called that are only based on some theoretical or mathematical construct of probability. They exist as a probable entities.

As such , the idea of them are based on some approximate guess or.hypothetical existencre.In other words they consist of pure thought until they can be perceived.

Thought without content may also be a possible vessel of energy which makes things possible sources of perception as they fill up with substance.

Marx cynically disallowed anything but the real substance or the substance of the real , and his reaction was parallel to the advent of anti idealism. His economic theory based on negating the substances of the unperceived played well with those to whom old ideals were a block to affirm new economic and political realities

That he was not so unique can be seen in other works like Spengler but Marx uses a falsely debunked system of Hegel, that had nowhere to go, in spite being an established mode of thought before Hegel and even Berkeley.

To blame Marx for carrying on the definition of what is substancetial, is to deny him at least the credible way he found a way out of an anti idealism. If for nothing else he deserves a place in the history of philosophy , albeit a mistaken one.